Apparatus for qualifying recorded tone bursts

ABSTRACT

Apparatus for qualifying recorded tone bursts on tape recordings. The apparatus includes connection means for connecting the apparatus to a tape player containing a tape with recorded tone bursts thereon so that the bursts from the tape are received in sequence by the apparatus. Filter means connected to the connection means for facilitating the acceptance of the upper frequency response of each tone burst. Amplifier means in connection with the filter means to provide for the gain loss in the filter means and accommodate the lower frequency response specification of the tone burst. Detector means are connected to the amplifier means and include means for providing a voltage that is indicative of the envelope of the tone burst. A first timing means set to time out just short of a predetermined minimum burst duration to produce a pulse in response to information from the detector means. A counter connected to the first timing means and responsive to the pulse therefrom to advance one counting unit. Latch circuit means connected to the detector so that a pulse therefrom resets a latch circuit set up at the beginning of a burst. A second timing means connected to the latch circuit to be initiated by the latch circuit and set to time out in excess of a predetermined minimum burst specification time. Alarm means connected to said second timing means so that when the latch circuit is not reset and the first timing means times out, an audible alarm is triggered indicating an acceptable burst. Finally, a third timing means is connected to the detector and the alarm means to time out if the pulse exceeds a predetermined maximum duration specification.

United States Patent Blethen Mar. 4, 1975 APPARATUS FOR QUALIFYING RECORDED TONE BURSTS Primary Eraminer-Bernard Konick Assistant E.raminerRobert S. Tupper Attorney, Agent, or Firml(ane, Dalsimer, Kane, Sullivan and Kurucz [57] I ABSTRACT Apparatus for qualifying recorded tone bursts. on tape recordings. The apparatus includes connection means for connecting the apparatus to a tape player containing a tape with recorded tone bursts thereon so that the bursts from the tape are received in sequence by the apparatus. Filter means connected to the connection means for facilitating the acceptance of the upper frequency response of each tone burst. Amplifier means in connection with the filter means to provide for the gain loss in the filter means and accommodate the lower frequency response specification of the tone burst. Detector means are connected to the amplifier means and include means for providing a voltage that is indicative of the envelope of the tone burst. A first timing means set to time out just short of a predetermined minimum burst duration to produce a pulse in response to information from the detector means. A counter connected to the first timing means and responsive to the pulse therefrom to advance one counting unit. Latch circuit means connected to the detector so that a pulse therefrom resets a latch circuit set up at the beginning of a burst. A second timing means connected to the latch circuit to be initiated by the latch circuit and set to time out in excess of a predetermined minimum burst specification time. Alarm means connected to said second timing means so that when the latch circuit is not reset and the first timing means times out, an audible alarm is triggered indicating an acceptable burst. Finally, a third timing means is connected to the detector and the alarm means to time out if the pulse exceeds a predetermined maximum duration specification.

1 Claim, 4 Drawing Figures APPARATUS FOR QUALIFYING RECORDED TONE BURSTS BACKGROUND OF THE INVENTION Audio visual aid systems have often been hampered by the necessity to handle and load two completely separate information media. For example, both an audio tape and film presentation can be provided in one small plastic cartridge. Both the audio tape and the film presentation can be provided on an individual endless loop with each loop housed inits own half of the cartridge.

This type of system centers around the premise that one picture is still worth a thousand words and that actual motion is seldom necessary to convey an idea. Therefore, given a picture and a few words of narration, the complete idea can be presented. Therefore, instead of having many hundreds of feet of motion picture film with sound, the same program can be presented more economically by separating the two media. In this manner, the system permits the film to be advanced only when necessary because the film is controlled by a tone burst recorded in synchronization, on tape, along with the audio portion of the program.

A physical relationship exists between each frame of the film and the location of the tone bursts recorded on the tape. For each frame, a tone burst exists to advance it. Other tone bursts of different frequency are used to stop the tape at the end of the program or a particular sequence and to control ancillary equipment. The bursts utilized in advancing the film frame-by-frame in synchronization with the audio program are very important. Consequently, it would be most advantageous to provide a method and apparatus to qualify these bursts as to their parameters in order to assure that the tape used in the cartridge will function satisfactorily in use.

SUMMARY OF THE INVENTION With the above background in mind, it is among the primary objectives of the present invention to provide a method and apparatus for qualifying properly recorded tone bursts on tape recordings. The type of bursts under analysis are those recorded on a control track accompanying audio material and which are used to synchronize various events in a low-cost audio visual machine. The apparatus is designed to check three important parameters of each burst. The parameters are amplitude, duration and frequency and the apparatus is designed to permit display of the total of all correct bursts. The apparatus is designed for easy use on site at the manufacturing facility to check any desired program as it is completed.

Specifications for the film advance signal include a burst 26 with a frequency being between 1K hertz and 1,600 hertz for a duration of 32.5 ms recorded at an amplitude of +3vu above standard record level. Although the tape speed in the exemplary tape system is l /8 inches per second (ips), standard recording level refers to that level which produces 200 nanowebers and not the level 6 db below this which is accepted as standard by some tape duplicators. Equalization used is 120 t see top and 1,590 1.1. sec low end roll-off used in the exemplary system.

The higher recording level is chosen primarily because of the hum and noise created by the inexpensive tape transport and lamp cooling fan motor in the machinery. therefore, without elaborate magnetic shielding, using the lower recording level does not provide sufficient signal-to-noise ratio which would also involve more sophisticated electronics. in the burst discriminator circuit. The discriminator circuit determines which burst is for film advance and which burst is for tape motion control.

In summary, a method and apparatus is provided for qualifying recorded tone burst on tape recordings. A connection means is utilized for connecting a qualifying apparatus to a tape player containing a tape with recorded tone bursts thereon so that the bursts from said tape are received in sequence by the apparatus. Filter means are connected to the connection means for facilitating the acceptance of the upper frequency response of each tone burst. Amplifier means are connected to the filter means to provide for the gain loss in the filter means and accommodate the lower frequency response specification of the tone burst. Detector means are connected to the amplifier means and include means for providing a voltage that is indicative of the envelope of the tone burst. A first timing means is set to time out just short of a predetermined minimum burst duration so as to produce a pulse. A counter is connected to the first timing means and is responsive to a pulse therefrom to advance one unit. Latch circuit means are connected to the detector so that a pulse therefrom resets a latch circuit set up at the beginning of a burst. A second timing means is connected to the latch circuit so as to be initiated by the latch circuit and is set to time out in excess of a predetermined minimum burst specification time. Alarm means are connected to the second timing means so that when the latch circuit is not reset and the first timing means times out, an audible alarm is triggered indicating an unacceptable burst. Finally, a third timing means is connected to the detector means and the alarm means and is arranged to time out if the pulse exceeds a predetermined maximum duration specification.

With the above objectives, among others, in mind reference is had to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a block diagram of the apparatus of the invention;

FIG. 2 is a schematic view of the circuitry employed in the apparatus of the invention;

FIG. 3 is a block diagram of the apparatus of the invention in conjunction with subordinate apparatus; and

FIG. 4 is a schematic view showing the relationship of the tape to a synchronized filmstrip.

DESCRIPTION OF THE PREFERRED EMBODIMENT For exemplary purposes, a tape, film synchronized system as discussed above which may be qualified by the present invention is depicted in FIG. 3 of the drawings. Method and apparatus of the present invention is equally applicable to similar tape film systems. In the system shown, the magnetic tape is a back lubricated 0.150 inch cassette tape 21. The track format utilizes a four-track arrangement with the first two adjacent tracks 22 and 23 being utilized for film audio narration and the fourth track 24for the control bursts. The third track 25 is not recorded, and the tape is recorded in one direction and spliced for endless loop operation.

The position of the control bursts on the tape 21 with respect to a filmstrip 27 is shown with the assistance of the arrows in FIG. 3. It will be noted that the bursts 26 are located at random distances on the tape travel and each burst 26 triggers advancement of the filmstrip 27 to the next available frame.

The general sequence of operations and elements utilized in the present invention is depicted in FIG. 1 of the drawings which primarily is directed to a block dia- I gram of qualifier 20. An input buffer stage 28 is provided at the point where qualifier initially receives the burst 26 from the tape. Buffer stage 28 is an emitter follower to prevent loading of the tape playback preamplifier to which qualifier 20 is connected. A level set control 29, as shown in FIG. 3, is on qualifier 20 to calibrate the qualifier to the playback machine when using an alignment tape with known burst amplitude. In describing the calibrating process, the signal must be followed from input buffer 28 through variable resistor 28' and, thereafter, through a three-pole low pass filter 29 and amplifier stages 30.

Low pass filter 29 actually sets the acceptance of the upper frequency response of the tone burst. Amplifier 30 following filter 29 serves to make up for the gain lost in filter 29 and to provide a 3 db per octave roll off in the low end gain. This accommodates the lower frequency response specification of the tone burst.

A connection to amplifier 30 output feeds a level indicator circuit 31. This circuit permits calibration of the equipment for'specified level from either a steady tone or from burst input. Two light-emitting diodes (LED) 32, 33 are set to break down and emit light at different burst amplitudes, allowing for a very simple level calibration. When bursts are used to set calibrate level, a persistency added to the LEDs allows the operator time to see which light or lights are activated. Since the bursts are only 32 ms long, this feature is quite valuable. With proper input level, the level set control is adjusted so that only one lamp is lit. If both lamps are lit, the control is adjusted until the high lamp 32 goes out, leaving only the calibrate lamp 33 lit.

The output of amplifier stage 30 also feeds detector 34. This stage detects and provides a voltage that is indicative of the bursts envelope. If the input burst is deficient in amplitude, or its frequency is out of specification, the detector output amplitude is modified accordingly.

The output of detector 34 feeds three timing circuits, two of which depend on the exact output voltage of the detector. The first timing circuit 35 is set to time out just short of the minimum burst duration. If the burst is correct, then the time out of circuit 35 causes a pulse to advance a counter 36 which totals the number of acceptable bursts. The pulse also resets 37 a latch circuit 38 set up by the beginning of a burst. Latch 38 starts the timing of the short burst timer 39 which is set for time out in excess of the minimum burst specification time. Latch 38 makes this circuit independent of detector output voltage. Once set up, latch 38 states simply that a burst has started and will be reset only if the minimum burst timer 35 times out. This is dependent upon minimum burst amplitude, burst tone frequency being within specification, and burst duration equal to or in excess of minimum specification.

If, however, latch 38 is not reset, short burst timer 39 times out, triggering an audible alarm 40 indicating an unacceptable burst.

A third timer 41 connected to detector 34 is set to time out and trip alarm 40 if the burst exceeds the maximum duration specification. This is an unusual situation because not only has alarm 40 been tripped, but minimum burst timer 35 has tripped counter 36 as well. This indicates that the last displayed number on counter 36 is actually a bad pulse, but with no indication that this is an exception. Since the counter 36 is not used to tally an exact count, except in the case where no alarm is sounded, this situation is acceptable. Although the alarm has sounded, counter 36 helps to pinpoint to within one burst the location by burst number, its whereabouts in the tape if the operator wishes to continue and to return to that point later. A script of the narration on the audio tracks along with all accompanying burst and burst numbers accumulated from the beginning is usually available.

Both maximum timer 41 and minimum burst timer 35 have their own reset stages 42 and 43 respectively. The reset circuit discharges the timing capacitor at the end of each burst.

Alarm stage 40 has three switches associated with it. The first switch is a reset push button switch 44 that allows the stage to be reset manually. The second switch is an auto reset toggle-switch '45, that when closed will reset the alarm stage if tripped by the next pulse of the minimum burst timer. The third switch is a toggle type 46 which, when closed, will clamp the output of detector 34 if the alarm stage is tripped. This action prevents the counter from receiving any further counts and al lows the operator to leave the equipment unattended. This same feature is also useful if the tape machine used with qualifier 20 has a remote stop which could be connected to alarm stage 40. Then, if the operator left the equipment and returned to find the alarm tripped and the tape machine stopped, he would known the bad burst was within a very short distance from the playback head. The-advantage of this feature is self-evident when a new burst must be dubbed in in place of the old.

Details of the specific circuitry in schematic form of the blocks of FIG. 1 is shown in FIG. 2 of the drawings.

Input buffer stage 28 is an emitter follower. Capacitors 40 and 41 are input and output coupling capacitors respectively. Resistors 42 and 43 serve to bias stage 28 and resistor 44 is the emitter resistor for transistor 45. Buffer stage 28 offers high input impedance to the tone burst from the tape playback electronics. Control 46 adjust the output of stage 38 which drives the three pole low pass filter 29. The low pass filter includes components resistor 47, resistor 48, resistor 49, capacitor 50, capacitor 51 and capacitor 52. Filter 29 is tuned to accept the upper frequency specification of the tone burst.

Amplifier stage 30 is used to make up for the low pass filter losses and to tailor the low frequency limit of the tone burst specification. Transistors 53 and 54 make up the high gain self-biased amplifier with associated components capacitor 55, resistance 56, resistance 57, resistance 58 and potentiometer 59. Resistor 60 and capacitor 61 set the low frequency gain. RC network capacitor 62 and resistor 63 provide negative feedback thereby setting AC gain and stability. Potentiometer 59 serves as a collector load resistor for transistor 54 and allows for setting the turn on or conduction point of transistor 64 in respect to the burst amplitude at the collector of transistor 54.

In regard to detector 34, capacitor 65 and resistor 66 serve as coupling and bias components respectively for transistor 64. Transistor 64 is normally biased on, therefore, its collector is near ground level and collector load resistor 67 for transistor 64 has full supply voltage dropped across it.

Transistor 64 is turned off by the negative transistions of the tone burst thereby removing the clamp from the anode of diode 68. With transistor 64 off, capacitor 69 is allowed to charge rapidly by current supplied through diode 68 and resistor 67. During positive transistions of the tone burst, the anode of diode 68 is clamped to ground which prevents charging current to flow. Diode 68 now serves to prevent capacitor 69 from discharging through transistor 64. Resistor 70 sets the relatively slow discharge time of capacitor 69 to approximately 2 /2 cycles of the burst frequency. Components including diode 68, resistor 70 and capacitor 69 serve as a detector circuit which detects the negative portion of the burst envelope.

During a tone burst, the cathode of diode 68 will see a DC voltage with a slight ripple caused by the fast charge, resistor 67 and the slow discharge, resistor 70 of capacitor 69. The amplitude of this voltage is indicative of the negative amplitude of the burst signal set by potentiometer 59 and the relative frequency of the burst signal. The burst signal frequency must fall within a region created by the low pass filter and the low frequency gain of the amplifier made up of transistors 53 and 54. lf the burst signal frequency does not fall within the proper band, then the level necessary to control transistor 54 will not be adequate and, therefore, capacitor 69 will not attain its full charge.

The cathode of diode 68 or the detector output feeds two timers, one timer 35 set for the minimum burst duration and the other timer 41 set for the maximum burst duration. Timers 35 and 41 operate from the voltage supplied from detector 34. This voltage at the top of potentiometer 71 supplies charging current for timer capacitor 72 in the minimum burst timer circuit. The potentiometer 71 sets the minimum burst time.

Minimum burst timer 35 uses a conventional programable unijunction transistor 72. Resistors 73 and 74 set the trigger parameters for transistor 72. Resistor 75 is a current limiting resistor and capacitor 72 and potentiometer 71 set the time out of the stage.

Timing begins when the burst envelope voltage builds up on the cathode of diode 68. The timer is set to trip or time out for the length of the minimum burst in this case ms. if the timing voltage supplied by detector 34 is maintained to allow the timer to trip, then the charge built up in capacitor 72 is dumped into resistor 75 thereby supplying a trigger to advance an electronic counter 36 by one count. This action indicates the burst is of minimum amplitude, within a proper frequency range and of minimum duration.

lf the frequency of the burst signal is not within limits and/or the amplitude is not of minimum specification set by potentiometer 59, then transistor 64 will not be fully turned off. Since the action of transistor 64 modulates the timer voltage, then capacitor 72 will take longer to charge and will not time out 30 ms after a burst is realized at the detector output.

Transistor 76 is used to reset the timing capacitor 72 when a burst duration or amplitude is not sufficient for transistor 72' to time out. Resistor 77 is used to bias transistor 76 off during a burst and on when no burst is detected. This reset stage assures that the timing cycle starts at the same point each time.

The second timer 41 and reset stage 42 connected to the output of detector 34 is set to time out when the maximum burst is not completed in time for transistor 78 to reset timing capacitor 79, then transistor 78 will trip the alarm stage 40 signaling a fault. The operation of the maximum burst timer 41 and reset circuit 42 is identical to that of the minimum burst timer 35 and reset stage 43.

Resistor 80, potentiometer 81, transistor 82, resistor 83, and resistor 84 provide the necessary component parts in similar as the respective components of the minimum burst timer 35 and reset stage 43.

At the collector of transistor 64 in detector stage 34, a connection is made and brought to a circuit which is designed to latch on when a signal is present at buffer input 28. The minimum signal necessary to activate the latch 38 is 6 db less than the minimum burst amplitude specification. The circuit of latch 38 once set is independent of the burst signal and is reset 37 by the time out of either the short burst timer 39 or the minimum burst timer 35.

The burst initiate latch 38 consists of a base current limiting resistor 67 for transistor 85, emitter load resistor 86, coupling capacitor 87, gate resistor 88, SCR transistor 89 and anode load resistor 90. Transistor 91 is also part of latch 38 with its emitter load and base resistor 92 and resistor 93 respectively.

The sequence of the circuit is as follows. If transistor 64 is turned off by the presence of an input signal, then transistor 85 is biased on. Current through transistor 85 develops voltage across resistor 86 and charging capacitor 94. Charging current for capacitor 87 through resistor 88 causes SCR transistor 89 to fire. The anode of SCR transistor 89 is now held near ground potential regardless of what happens at the collector of transistor 64. Resistor 93 connected between the anode of transistor 89 and the base of transistor 91 then allows transistor 91 to turn on', dropping near full supply voltage across resistor 92. Transistor 91 is held on by the latch 38 and allows timing capacitor 95 to charge through trimmer potentiometer 96 used to set the time out of the short burst timer transistor 97. 7

SCR transistor 98 is used to reset latch circuit 38. This is accomplished if the minimum burst timer 35 times out which provides a trigger via capacitor 99 to fire transistor 98. SCR transistor 98 serves to commutate SCR transistor 89 off when SCR transistor 98 is turned on. If minimum burst timer 35 does not reset latch circuit 38, then the short burst timer 39 times out and fires the alarm 40. This indicates that a burst of less than minimum duration has occurred.

Short burst timer 39 is a programable unijunction transistor 97 and its associated components resistor 100, resistor 101, resistor 102, and timing elements control potentiometer 103 and capacitor 95. This circuit operates in the same manner as the minimum burst timer 35 except in the manner its timing capacitor is reset in the event that it does not time out. The latch reset circuit 37 also resets the short burst timing capacitor 95 by way of diode 104 connected between capacitor 95 and the anode of transistor 98.

In operation, the short burst timer 39 is turned on by the burst initiate latch 38. Timer 39 is set to time out two ms after the minimum burst timer 35 which will not time out when a short burst is present. If however the incoming burst is proper in respect to amplitude and minimum duration, then the minimum burst timer will fire and reset latch 38 and the short burst timing capacitor clearing both for the next burst.

An SCR is used to activate alarm 40 which is a commercial device that produces a loud scream when voltage is supplied to it. The alarm SCR transistor 105 is triggered by either the maximum burst timer 41 or the short burst timer 39. Resistor 106 is used to maintain holding current for transistor 105 which will continue to conduct and activate alarm 40 until reset by momentary push switch 107.

Toggle switch 108 connects the anode of alarm SCR transistor 105 to a commutating capacitor 109 connected to the latch reset SCR anode. This switch when closed will reset the alarm SCR if on by the next burst that allows the minimum burst timer 35 to time out and trigger the latch reset circuit 37. This type alarm will give an indication of trouble only for the period of time separating a bad burst and the conformation of the next good burst.

Toggle switch 110, if closed, will connect the anode of transistor 105 of the alarm SCR to the collector of transistor 64 in detector stage 34. When this switch is closed and the alarm is fired the collector of transistor 64 is clamped to ground subsequently preventing any further burst to be evaluated and locking the counter 36 to the number representing the last good burst. In the case of a bursthaving excess duration, lelss than mild duration or low amplitude with switch 110 closed then counter 36 will represent the last count at the burst.

There is one last connection made to the anode of transistor 105 and this is used to gate a signal to a storage oscilloscope 156 which is in the single sweep mode. The oscilloscopes vertical amplifier is fed from a magnetic pick-up head positioned down stream from the head used to sense the input for the qualifier 20. The mechanical spacing is set in a way that the oscilloscope will only trace and store for evaluation a burst previously qualified ,and determined bad. Contacts positioned on switch 107 are used to erase the storage tubev and ready the oscilloscope to capture the next bad burst.

The level indicator stage 31 is necessary to calibrate the equipment for burst amplitude. Control potentiometer 46 is a sensitivity control and is set while test bursts are supplied to the input. The proper setting is attained only when the LED marked calibrate flashes during a burst. If the Hi LED also lights during a burst then potentiometer 46 must be reduced for a burst to activate only the calibrate LED.

Operation of the level indication circuit depends upon where potentiometer 1 11 is set which determines the calibration level for that LED to emit. Capacitor 112 is a coupling capacitor and resistor 113 bases transistor 114 off between bursts. Transistors 114 and 115 are connected in darlington fashion for a high input impedance at the base of transistor 114 and a low output impedance at the emitter of transistor 115. Capacitor 116 is charged rapidly when transistor 114 is turned on by a burst and this turns on transistor 115 as wellj Capacitor 116 discharges slowly through resistor 117 and the base emitter junction of transistor 115. The peak value of the expodential decaying voltage across resistor 117 determines whether both transistor 118 and transistor 119 or only transistor 119 are biased on. If

the voltage is great enough at the emitter of transistor then diode 120 will be forward biased by current through resistor 121 and resistor 121' and transistor 119 will conduct. Current flowing through resistor 122 and light emitting diode 123 will cause light to emit from diode 123 indicating the burst is of proper amplitude. Since the burst in this case is approximately 35 ms in duration, capacitor 1 16 adds a persistency quality to the LED light. This allows for setting of potentiometer 46 while using only random burst as an input for amplitude.

If however the burst amplitude is in excess of the calibrate level, then current will flow through resistor 122 zener diode 124 and resistor 124'. This will forward bias transistor 118 causing LED diode 125 to light from current flowing through it and resistor 125 to the collector of transistor 118. Resistor 125' is a current limit resistor for diode 125.

The components including resistor 80, potentiometer 81, transistor 82, resistor. 83, resistor 84, transistor 78 and capacitor 79 make up the maximum burst timer and reset circuit and operate exactly as does the minimum burst timer and reset.

Capacitor 89 is a commutating capacitor used to turn off either transistor 89 or transistor 98 depending on which one is conducting.

Resistor 88 is the load resistor for SCR transistor 98 and resistor 98 is the gate bias resistor for transistor 98.

If the amplitude of the voltage at the emitter of transistor 115 is in excess of the calibrate value, diode 124 is also forward biased. The breakdown of diode 124 junction is chosen 4 db greater than diode 120 which allows for a production tolerance in the burst amplitude. When diode 124 is forward biased then transistor 125 is turned on and LED diode 125 emits indicating an excess of level.

For a more complete understanding of bad bursts and their causes, qualifier 20 is adapted for use in a system as shown in FIG. 3 designed to detect bad bursts and to store and display them on a storage oscilloscope 156. System 140 includes a tape playback machine 141 with a special head constructed with two separate cores 142 and 143 located to read the control track 24. The spacing 144 between the two core gaps is chosen for qualifier 20 to evaluate the burst read by the first gap 142 before it is seen by the second gap 143. The head acts as a delay line.

Playback machine includes a feed reel 145 for the tape and a take-up reel 146. The tape is fed from reel 145 around post 147 through the pick-up heads and then around post 148 to the pick-up reel 146. The audio program on tracks 22 and 23 of tape 21 are passed through a preamplifier system 150 into a power amplifier 151 and then into speaker 152 for audio reception.

The control track signal picked up by gap 142 is passed through a preamplifier 153 and fed into the qualifier 20. If the burst is determined to be incorrect by qualifier 20, then the alarm system amplified by preamplifier 154 closes a gate 155 that couples the second core 143 of the playback head into a storage scope 156. Scope 156 is set in single trace mode while the trace threshold is set sufficiently high to prevent noise from triggering it. Erase and single trace circuitry within the oscilloscope is tied 157 to the alarm reset button 158 in qualifier 20. This feature is provided so that the operator can push one button instead of three to continue processing. lfdesired, a second reset button can be provided so that the audiblcalarm can be shut offwhile allowing display observation.

Thus, the above discussed objectives of the invention, among others, are effectively attained.

I claim:

1. Apparatus for qualifying recorded tone bursts for a predetermined desirable amplitude, frequency specification, and duration on tape recordings comprising:

connection means for connecting the apparatus to a tape player containing a tape with the recorded tone bursts thereon so that the bursts from the tape are received in sequence by the apparatus;

a buffer stage means in the apparatus to receive each tone burst and provide high input impedance to the tone burst and having control means thereon to ad just the output thereof;

a low pass filter means connected to said buffer stage means and tuned to accept the upper frequency specification of the tone burst;

an amplifier means connected to the filter means to make up for the low-pass filter means losses and to tailor the low frequency limit of the tone burst specification;

a detector means connected to the amplifier means and sensitive to the burst signal frequency created by the low-pass filter means and the amplifier means to supply an output voltage;

first and second timer means connected to said detector means and providing an output responsive to the presence of said output voltage for their time out periods;

the first timer means being set to time out at the predetermined minimum acceptable burst duration and the second timer means set to time out at the predetermined maximum acceptable burst dura- 10 tion;

the first timer means having adjustment means for varying the time out period;

a counter means connected to the first timing means whereby when the voltage supplied by the detector means is of sufficient duration for the first timer means to time out and provide said output it will trigger the counter means by one count thereby indicating the burst is of minimum amplitude, within a proper frequency range and of minimum dura tion;

reset means connected to the first timer means for resetting said first timer means when a burst duration or amplitude is not sufficient for the timer to time out;

reset means connected to the second timer means for'resetting said second timer means when a burst duration or amplitude is not sufficient for the timer to time out;

a latch circuit means interconnected with the detector means for latching on responsive to said output voltage;

latch reset means for resetting said latch means responsive to the timing out ofeither said first or sec ond timer means;

a third timer means interconnected with the latch circuit means and set to time out at a predetermined time less than the predetermined minimum acceptable burst duration and providing an output responsive to said latch means being latched on for said predetermined time less than the predetermined minimum acceptable burst duration; and

the alarm stage means for producing a signal responsive to said output of either said second or third timer means 

1. Apparatus for qualifying recorded tone bursts for a predetermined desirable amplitude, frequency specification, and duration on tape recordings comprising: connection means for connecting the apparatus to a tape player containing a tape with the recorded tone bursts thereon so that the bursts from the tape are received in sequence by the apparatus; a buffer stage means in the apparatus to receive each tone burst and provide high input impedance to the tone burst and having control means thereon to adjust the output thereof; a low-pass filter means connected to said buffer stage means and tuned to accept the upper frequency specification of the tone burst; an amplifier means connected to the filter means to make up for the low-pass filter means losses and to tailor the low frequency limit of the tone burst specification; a detector means connected to the amplifier means and sensitive to the burst signal frequency created by the low-pass filter means and the amplifier means to supply an output voltage; first and second timer means connected to said detector means and providing an output responsive to the presence of said output voltage for their time out periods; the first timer means being set to time out at the predetermined minimum acceptable burst duration and the second timer means set to time out at the predetermined maximum acceptable burst duration; the first timer means having adjustment means for varying the time out period; a counter means connected to the first timing means whereby when the voltage supplied by the detector means is of sufficient duration for the first timer means to time out and Provide said output it will trigger the counter means by one count thereby indicating the burst is of minimum amplitude, within a proper frequency range and of minimum duration; reset means connected to the first timer means for resetting said first timer means when a burst duration or amplitude is not sufficient for the timer to time out; the reset means connected to the second timer means for resetting said second timer means when a burst duration or amplitude is not sufficient for the timer to time out; a latch circuit means interconnected with the detector means for latching on responsive to said output voltage; latch reset means for resetting said latch means responsive to the timing out of either said first or second timer means; a third timer means interconnected with the latch circuit means and set to set time out at a predetermined time less than the predetermined minimum acceptable burst duration and providing an output responsive to said latch means being latched on for said predetermined time less than the predetermined minimum acceptable burst duration; and the alarm stage means for producing a signal responsive to said output of either said second or third timer means. 